Offshore oil and gas pipelines leading from stationary marine structures to the shore are widely used, and they serve as vital links in the fuel production process, transporting fossil fuels from drill sites to production facilities. There are a vast number of offshore platforms, oil wells, and mining rigs, for example, located in coastal water oil fields throughout the world, and pipelines are used to deliver the oil and natural gas from these offshore platforms to holding tanks on land. Each time a pipeline crosses another pipeline a separation of the two must be maintained. The pipelines must also be stabilized in high-current areas, and all unburied pipelines must be protected from the possibility of impact damage. Also, there may be a need to add support to a depressed area in the sea floor before a pipeline or valve station is installed. The underwater valve stations and pipelines must be protected from trawling shrimp boat boards, etc. For convenience of maintenance and repair of the pipelines, the protective covering must sometimes be removed. Conventional methods of protecting the pipelines include concrete mats and burlap bags.
Concrete mats include a series of interconnected concrete hexagonal blocks connected together with polypropylene rope to form a concrete mattress. In essence, concrete mats are solid concrete blocks located within a rope-like netting. There are two different standard size concrete mats consisting of 160 block segments that are laced together with approximately 400′ of polypropylene rope. The two standard sizes are 8′×20′×4½″ and 8′×20′×9″.
The larger size concrete mat (8′×20′×9″) is used primarily on the ocean floor. The concrete mats, while jointed, due to the rope connections between concrete blocks, have an essentially rigid nature, and proper alignment during construction is critical. The 160 cement block segments become very heavy at 10,500 lbs. each and only 4 mats can be trucked at one time to it shipping location. The structure of the concrete mats also makes them very awkward to handle, requiring a heavy constructed lifting spreader bar with 20 slings pick-up to lift the concrete mat from the truck to the boat. This same lifting spreader bar is required offshore. The boat is limited on the number of mats it can carry due to these heavy weight items.
Offshore, the same hook-up is required to lift the concrete mat and lower it into the water. Divers are required to direct the lowering of the mat onto its destination. Once the concrete mat is properly aligned, the divers must unhook all 20 lifting slings. In low visibility dive conditions, occasionally divers will mistakenly leave one or more of the slings connected when the boat raises the spreader bar and the concrete mat will be pulled out of position, becoming useless so that it must be re-hooked and moved back to its correct location (with additional effort and safety concerns). Furthermore, ocean surges during deployment of the mat (which traps water in the mat, causing an up and down flexing of the mat while it is being lowered into the water, and which results in a rocking motion in the deploying boat), increase both the complexity and the danger associated with the deployment maneuver. This ocean surging effectively adds weight to the concrete mat and to the boat crane, and is very dangerous for the divers when a downward 8′ ocean surge can bring a 10,500 lbs. concrete mat onto a diver in a split second. The complex installation issues involved with concrete mats have caused the diving industry to generally dislike them.
Burlaps bags are the oldest method of protecting pipelines used on the ocean floor. These 60 lbs. burlaps are filled with pure sand or sand/cement at a sand plant. The burlap bags are then typically stacked 56 bags per wooden pallet and shipped 14 or 15 pallets per truck. The pure sand or sand/cement burlap bags are lowered into the ocean by cargo nets and the divers place the burlaps into position. The difference between the two is that the pure sand does not harden, while the sand/cement turns into concrete after 4 hours. Both burlaps take's the shape of what they are settling on. Many times the burlaps are used with the concrete mats to form a better seal. The pure sand burlaps are required as a temporary installation while the sand/cement burlaps are on the permanent side. Both pure sand and sand/cement burlaps are more cost effective than the concrete mats, but are more labor intensive, requiring more time to position the individual bags. And while burlap bags with cement will harden to take the permanent shape of their area, they are more difficult to reapply in a manner which ensures a secure fit, due to their size and shape. Finally, burlap does not provide a durable covering, as it will decay over time. So, burlap bags are not recommended when permanence or removal is an important factor. The present invention of the BulkMat is intended to provide a simple and effective means to install pipeline protection of a more permanent nature, which conforms precisely to the shape of the area it is covering and holds the shape so that it may also be removed and reapplied again to ensure a secure fit.